Anodic printing by means of a hydrogen ion sensitive precipitation reaction



Aug. 27, 1968 G. P. KLEIN 3,399,121

ANODIC PRINTING BY MEANS OF A HYDROGEN ION SENSITIVE PRECIPITATION REACTION Filed Nov. 18, 1964 2 Sheets-Sheet 1 INVENTOR. GERHART P. KLEIN BY i ATTORNEY Aug. 27, 1968 G. P. KLEIN 3,399,121

ANODIC PRINTING BY MEANS OF A HYDROGEN ION SENSITIVE PRECIPITATION REACTION Filed Nov. 18, 1964 2 Sheets-Sheet 2 IMPREGNATE IMPREGNATE wn'n ALCOHOLIC WITH CHROMATE SOLUTION OF AN SOLUTION AMINE DERIVATIVE OF asnzmmz REMOVE EXCESS SOLUTION DRY PAPER DRY PAPER APPLY CHROMATE SOLUTION WITH pH OF 6.9 IMPREGNATE WITH ALCOHOLIC SOLUTION OF AN AMINE DERIVATIVE OF BENZIDINE PARTIALLY DRY DRY PAPER ELECTRODE PRINTING WRITE WITH DILUTE ACID INVENTOK .GERHART P KLEIN FM ATTORNEY United States Patent-O ANODIC PRINTING BY MEANS OF A HYDROGEN ION SENSITIVE PRECIPITATION REACTION Gerhart P. Klein, Manchester, Mass., assignor to P. R.

Mallory & Co., Inc., Indianapolis, Ind., a corporation of Delaware Filed Nov. 18, 1964, Ser. No. 412,164

4 Claims. (Cl. 204-2) ABSTRACT OF THE DISCLOSURE A recording media consisting of a paper sheet impregnated with an aqueous solution of potassium chromate and an alcoholic solution of o-tolidine.

The present invention relates to recording media and more particularly relates to a paper which becomes discolored or otherwise marked by the passage of an electric current therethrough.

In the art of marking or recording by means of ap plied electric voltages, for example, in the art of facsimile recording on electrochemical blanks, usually of paper, the recording mark is made by locating the blank while in a suitably moistened condition between a pair of electrodes across which the signal voltages are applied. Usually, both electrodes are in contact with the blank so as to produce a complete conductive path through the thickness of the blank. The electrodes may be in the form of intersecting knife edges, one of which maybe a helical knife edge on a rotary drum, and the other a cooperating straight knife edge; the two knife edges intersecting to define a conductive region of elemental size. The current flow through the blank brings about the liberation or concentration of ions at one of the electrodes, and these ions are responsible for the development of a color contrast or mark on the surface of the blank. The marking operations can be effected in a variety of ways well known in the art.

One object of the present invention is to provide an improved form of electrographic recording medium. The recording blank or medium should be highly sensitive to electric current, producing easily recognizable marks when activated by a comparatively weak current. It should be capable of producing clear marks of high definition with aminimum of fringes, which are stable and persist over a reasonable length of time. The marks should be of a pleasing color on a background of equally pleasing color which may be manufactured with ease and safety with materials readily obtainable through ordinary channels of commerce, and which may be handled without excessive precautions in that it is not unduly sensitive to ordinary daylight. It is further desirable that the recording blank not require any development of fixation process subsequent to use in order for it to remain insensitive to light and not discolor after standing or even after being repeatedly run through any of the conventional duplicating machines involving exposure to ultra-violet light.

Another very important consideration is the provision of a recording paper wherein the marking compound or other active ingredients in the paper will not diffuse or transfer, during or after recording, to adjacent sheets or surfaces of marked or unmarked paper nor to adjacent areas such as the walls of the recorder cabinet or of the room itself. Such transfer frequently results in an objectionable discoloration of the adjacent paper, surfaces and walls.

It is, therefore, an object of the present invention to provide improved electro-responsive graphic recording means.

It is an object of the present invention to provide 3,399,121 Patented Aug. 27, 1968 electro-sensitive recording media containing as a marking compound, a compound which heretofore has not been employed for this purpose.

It is an object of the present invention to provide a new electro-sensitive recording media wherein there is no external diffusion or transfer of the ingredients of media during or after recording.

It is a further object to provide electrolytic recording media which is chemically stable prior to use and which will remain stable to light and air of varying humidity both during and after recording.

The present invention in another of its aspects, relates to novel features of the instrumentalities of the present invention described therein for teaching the principal object of the present invention and to the novel principles employed in the instrumentalities whether or not these features and principles may be used in the said object or in the said field.

With the aforementioned objects enumerated, other objects will be apparent to those possessing ordinary skill in the art. Other objects will appear in the following description, appended claims and appended drawings. The invention resides in the novel construction, combination, arrangement and cooperation of elements as hereinafter described and more particularly as defined in the appended claims and taken in conjunction with the accompanying drawing in which:

FIGURE 1 is a perspective view of the recording medium and a simplified marking means illustrating a principle of the invention when utilizing electrolytic printmg.

FIGURE 2 is a sectional view of the impregnated paper showing the relationship of the paper to the printed mark.

FIGURE 3 is a perspective view of the recording medium and a simplified marking means illustrating the writing with acid.

FIGURE 4 is a sectional view of relationship of the paper to the printed mark obtained with acid printing.

FIGURE 5 is a flow chart of the method of impregnation for electrode printing.

FIGURE 6 is a flow chart of the method of impregnation for acid printing.

Generally speaking, the present invention provides electrolytic recording media wherein the production of hydrogen ions from an electrode reaction causes a color precipitation of a blue to black compound in the writing medium. The resultant precipitation produces a sharp trace which does not diffuse, and which is waterproof. The present invention further allows writing with dilute acids wherein the slightly acidic writing fluid produces the desired reaction while precluding the clogging of the pen system which is frequently encountered with recorders using ink.

The writing medium for pen writing is prepared from two solutions: an aqueous solution of potassium chromate or any suitable chromate in concentrations ranging from 1-100 grams/liter, with 15-25 grams/liter being preferred, depending upon the particular application; and an alcoholic solution of o-tolidine or similar amine derivatives of bensidine in concentrations of 10-40 grams/liter with 10-25 grams per liter being preferred. A suitable paper is dipped into solution 1, and the excess solution is removed. The paper is then dried, dipped into solution 2 and redried. Any pen or pen system is filled with a dilute acid, such as 1-5 acetic acid.

For electrode printing purposes, the paper is first dipped into solution 2, dried and then dipped into solution 1, which has been adjusted to a pH of 6.9. After partial drying, the paper is ready for electrode printing wherein a counter electrode is required along with the writing electrode. A sheet of meal such as copper, aluminum, etc. is well suited for a counter electrode. A platinum tip may serve as the writing electrode. The electrodes are connected to a DC voltage source of at least 2 volts, the electrode reaction taking place at the writing electrode (the anode) is the evolution of oxygen according to the equation:

The formation of hydrogen ions changes the pH locally towards more acidic values. This causes the precipitation of a black compound of chromate ions with o-tolidine. The precipitation point of the compound is just outside the buffer range of the chromate-dichromate system so that the electrolyte is very sensitive to hydrogen ions.

Referring to FIGURE 1, there is shown a recording medium 10, usually a porous paper, which is rendered conductive by impregnation with the solution as hereinbefore described. Recording medium 10 is supported on plate 11 of metal or other conducting material and is held in place by holding clip 12 which is optional. The pencil or stylus 13 as assumed to be movable so that it may be placed under the recording medium 10 at any point at which it is desired to mark. Plate 11 and stylus 13 are connected to a source of electric current 14 so that a current flows through the chromate-tolidine solution when the stylus is touched to the paper. At any point, the solution will undergo a change from mauve to black and thus any desired legend may be written upon the recording medium 10 by suitably moving stylus 13 thereover. Although recording medium 10 is shown as a fiat sheet in FIGURE 1, it preferably should be of a flexible nature so that it may be rolled.

In FIGURE 2 there is shown a cut-away view of recording medium 10 showing the precipitated printing .15 which is formed on the paper. Most recording mediums undergo a change when cont-acted by an electric source which forms a colored dye. The present invention, however, forms a solid at the point of contact with the electrode and this solid adheres firmly to the paper, thus eliminating the spread normally obtained by conventional printing means and allowing sharp, clear traces to be obtained.

In FIGURE 3, there is shown an embodiment of the invention wherein the marks are produced by utilizing an acid-filled pen. Recording medium 16 which has been impregnated with the aforementioned hydrogen ion sensitive solution is contacted by pen 17 which contains a dilute acid such as percent acetic acid. Trace 18 is formed wherever pen 17 contacts the recording meduim 16. In FIGURE 4 the relationship between the writing medium 16 and the solid printed mark 18 produced by pen contact 17 is shown. It can be seen that pen 17 contains the acid solution 19, said acid producing the necessary pH change as it contacts medium 16 to produce mark 18.

In FIGURE 5 a flow chart explaining one method of impregnating the writing medium with the Writing compound is shown. In FIGURE 6 a flow chart showing one method of impregnating the writing medium for acid writing is shown.

The embodiments as herein before described represent two aspects of the present invention. However, certain variations may be practiced without departing from the scope of the invention and will be readily apparent to those skilled in the art. For instance, the present invention may be applied to any printing system utilizing electrode printing and may further be used in cases where inks or dye are currently used. I consider all of these variations and modifications to be within the foregoing description and defined by the appended claims.

Having thus described my invention, I claim:

1. An electrolytic recording medium comprising an impregnated sheet, said sheet containing as a marking compound an alcoholic solution of 10-40 grams per liter, 0- tolidine and an aqueous solution of 1-100 grams per liter of potassium chromate in an electrically conducting system in which the pH of said impregnate is about 69, said impregnate being sensitive to an increase in hydrogen ion concentration and forming a colored precipitate therewith.

2. An electrolytic recording medium comprising an impregnated sheet, said sheet containing as a marking compound an alcoholic solution of 10-25 grams per liter of otolidine and 15-25 grams per liter of potassium chromate in an electrically conducting system in which the pH of said impregnate is about 6.9, said impregnate being sensitive to an increase in hydrogen ion concentration and forming a colored precipitate therewith.

3. A recording medium comprising an impregnated sheet, said sheet containing as a marking compound an alcoholic solution of 10-40 grams per liter, o-tolidine and an aqueous solution of 1-100 grams per liter of potassium chromate in an electrically conducting system in which the pH of said impregnate is about 6.9, said impregnate being sensitive to an increase in hydrogen ion concentration and forming a colored precipitate therewith.

4. A recording medium comprising an impregnated sheet, said sheet containing as a marking compound an alcoholic solution of 10-25 grams per liter of o-tolidine and 15-25 grams per liter of potassium chromate in an electrically conducting system in which the pH of said impregnate is about 6.9, said impregnate being sensitive to an increase in hydrogen ion concentration and forming a colored precipitate therewith.

References Cited UNITED STATES PATENTS 1/ 1957 Schwartz 204-2 2/1964 Mandet 204-2 

